In a manufacturing of a semiconductor device, various processes such as film formation, etching and the like are repeatedly performed on a semiconductor wafer to manufacture a desired semiconductor device. Recently, in order to meet demands for high-speed semiconductor device, miniaturization of a wiring pattern and high level of integration, it is required to realize low resistance of wiring (high conductivity) and high electromigration resistance.
In view of the above, Copper (Cu), which has a higher electromigration resistance and a higher conductivity (lower resistance) than those of aluminum (Al) and tungsten (W), is being used as the wiring material.
The Cu wiring is formed by filling Cu in a trench or via formed in an interlayer insulating film. However, in order to prevent Cu from being diffused in the interlayer insulating film, a barrier film is formed before filling Cu.
As for a method of forming the barrier film, there is used a method of forming a tantalum (Ta) film, a titanium (Ti) film, a tantalum nitride (TaN) film, a titanium nitride (TiN) film or the like by physical vapor deposition (PVD). However, with a further miniaturization of a wiring pattern, it is difficult to obtain a sufficient step coverage by the above-mentioned method. Accordingly, there is examined a method of forming as the barrier film a manganese oxide (MnOx) film by chemical vapor deposition (CVD) or atomic layer deposition (ALD) which can form a thin film with a good step coverage. Since, however, the MnOx film has low adhesion to Cu film, there has been proposed a Cu wiring forming method in which a Ruthenium (Ru) film having high adhesion to Cu film is formed as a liner film on the MnOx film and a Cu film is formed on the Ru film (see, e.g., Japanese Patent Application Publication No. 2010-21447).
Meanwhile, when the Ru film is formed on the MnOx film, it is difficult to obtain the Ru film having a good surface state due to a low nucleus formation density of Ru. Accordingly, there has been proposed a technique in which a hydrogen radical process (hereinafter, referred to as “H2 radial process”) is performed after the MnOx film is formed and then the Ru film is formed thereon (see, e.g., PCT Publication No. 2012/173067).
However, with a further miniaturization of a semiconductor device, a ratio of a cross sectional area of the barrier film and the liner film to a cross sectional area of Cu wiring is increased. As a result, a wiring resistance is increased.